The present invention relates generally to valves for controlling fluid flow and relates more particularly to a valve plug and seat assembly adapted for use with fluids containing dirt, minerals or other materials likely to foul conventional valve surfaces. The present valve plug and seat assembly is particularly well suited for use with steam condensate drain systems.
In a conventional steam condensate discharge valve which the present valve plug and seat assembly is designed to replace, the valve plug comprises a conical element adapted to cooperate with a frusto-conical valve seat. Actuating means are provided for automatically moving the valve plug toward and away from the valve seat to control flow through the valve.
Although the described conventional valve initially works well, after continuous use and particularly under conditions in which the valve is open for substantial periods of time, dirt or minerals become deposited on the valve surfaces and prevent the fluid-tight seating of the valve plug. Valve leakage results and can only be corrected by disassembly and cleaning or replacement of the plug and seat elements. A leaking valve permits a continuous escape of steam and a costly waste of energy.